Apple's stock dropped 2.4 percent to $439.51 in midday trading Friday for a market capitalization of $412.7 billion. That followed a 12 percent drop on Thursday, the biggest one-day percentage drop for the company since 2008.
Exxon Mobil Corp. gained 22 cents Friday to $91.57 for a market capitalization of $417.5 billion.
Apple first surpassed Exxon in the summer of 2011, displacing the oil company from a perch it had held since 2005. The two companies traded places through that fall, until Apple surpassed Exxon for good in early 2012 — at least until Friday.